Cell cycle and Reproduction. BIO… LIFE…. THINK ABOUT THIS: What do we do in our lifetime? What...
Transcript of Cell cycle and Reproduction. BIO… LIFE…. THINK ABOUT THIS: What do we do in our lifetime? What...
Cell cycle and Reproduction
BIO…LIFE….
THINK ABOUT THIS:
What do we do in our lifetime?
What are the major stages of our life?
What are the Major stages of physical development in our lives? What would it look like
if we put this into a pie
chart?
Cell cycle: repeating sequence of cellular growth and division during the life of an
organism; check points trigger the next stage of the cycle
The life of a cell Cells have a life cycle just like we do- born, grow, reproduce,
and die. They only spend part of
their life cycle reproducing (M)- mitosis
Imagine you are a bacteria:What are the major stages in your life?
TRY ME: What is A? B? C? What is D/E/F/G collectively
called? What is D? What is E? What is F? What is G?
https://www.youtube.com/watch?v=65SODTL_QsA
Figure 9-8 The eukaryotic cell cycle
G1: cell growth and differentiation
telop
hase an
dc
yto
kin
es
is
anap
hase
metaphase
prophase
S: synthesis of DNA; duplication of chromosomes
G2: cell growth and preparation for cell division
Cell Cycle
1. Interphase (G1, S, G2) – cell grows, prepares to divide (G phases) and DNA replicates (S phase)
2. Mitosis: nucleus divides; each nuclei winds up with the same # and kind of chromosomes as the parent (P-M-A-T)
3. Cytokinesis: division of cytoplasm
WHY DO CELLS DIVIDE?WHY DO THEY DO MITOSIS???
UNICELLULAR vs. MULTICELLULAR?
Why do cells divide?
UNICELLULAR
To reproduce (asexual reproduction)- budding/binary fission Ex. Bacteria hydra
vs. MULTICELLULAR? Grow Repair/replace cells that have been lost or damaged
Let’s think a second:THINK: Why do we have cycles and cells split? Why doesn’t the cell just get bigger and bigger?
Which turtle has bigger cells?
Neither!!!
Their cells are the same size… this one just has MORE!
Why don’t cells continue to grow?
There are two main reason why cells divide instead of continue to grow:
1. The larger the cell becomes, the more demands the cell places on its DNA
2. The cell has more trouble moving enough nutrients and wastes across the cell membrane.
DNA “Overload” Information that controls a cell’s function is stored in a
molecule knows as DNA In eukaryotic cells, DNA is found in the nucleus
DNA “Overload” When a cell is small, the information stored in the DNA is
able to meet all of the cell’s needs If a cell was too large an “information crisis” would occur and
the cell would not function properly
Example: Small library in a large city
Exchanging Materials
Food, water and nutrients enter the cell through its cell membrane
Waste products leave in the same way
Exchanging Materials
Example: Small streets in a big town
Exchanging Materials The relationship between a cell’s volume and its surface
area is the key to understanding why cells must divide as they grow!
Ratio of Surface Area to Volume
Ratio of Surface Area to Volume
The volume increases much faster than the surface area, causing the ratio of surface area to volume to decrease.
This decrease creates serious problems for the cell.
Formula for calculating ratio:
Ratio = Surface Area/Volume
SPLIT GROUPS: FIND SA , Volume and ratios for
3x3, 5x5, 8x8, 10x10
Lab surface/volume ratio
CAN WE FIND THIS EXPERIMENTALLY???
FIND SA , Volume and ratios for
For: 3x3, 5x5, 8x8, 10x10
Problem: What happens to the surface/volume ratio when a cube gets really big?
Hypothesis:
Methods:
Result table in excel:
Conclusion:
So what happens when cells get TOO LARGE????
THEY SPLIT- MITOSIS.
DNA replicates in interphase?Which part of cell cycle???
What happens in each:PROPHASEMETAPHASE ANAPHASETELOPHASEhttp://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#
no cell wall cell wall
Mitosis
46chromosomes
92chromosomes
46chromosom
es
46chromosom
es
parent cell
daughter cells
AMEOBA SISTERS: https://www.youtube.com/watch?v=gwcwSZIfKlM&list=PLwL0Myd7Dk1F1pp-DaLx3ygO_7xA-yyd4&index=3
BUT WHY CELLS DON’T JUST SPLIT ALL THE TIME????
Or in other words….
What happens if things go wrong with checkpoints?
THINK ABOUT THIS!!!!
Loss of Control of the Cell Cycle
If checkpoints are not working properly, the cell cycle can cause the cell to grow
uncontrollably
leads to cancer .
THINKING QUESTION:What biomolecule controls checkpoints?
AMEOBA SISTERS: https://www.youtube.com/watch?v=lpAa4TWjHQ4&list=PLwL0Myd7Dk1F1pp-DaLx3ygO_7xA-yyd4&index=2.
And what controls the making of proteins? DNASO WHAT’S THE DIFFERENCE BETWEEN PROKARYOTIC AND EUKARYOTIC DNA
How Is the DNA in Eukaryotic Chromosomes Organized?
Eukaryotic chromosomes differ from prokaryotic chromosomes in important ways Eukaryotic chromosomes are separated from the
cytoplasm by a membrane-bound nucleus Eukaryotic cells always have multiple chromosomes Eukaryotic chromosomes are longer and have more
DNA than prokaryotic chromosomes (human chromosomes are 10 to 80 times longer and have 10 to 50 times more DNA)
These differences account for the complexity of eukaryotic cell division
How Is the DNA in Eukaryotic Chromosomes Organized?
The eukaryotic chromosome consists of a linear DNA double helix bound to proteins
Each human chromosome contains a single DNA double helix, about 50 million to 250 million nucleotides long
Most of the time, the DNA in each chromosome is wound around proteins called histones These DNA-histone spools are further folded into coils Another layer of folding occurs as the coiled strand folds into loops, which are then
attached to protein scaffolding, so that the chromosome is 1,000 times shorter than the extended DNA molecule
During cell division, more proteins fold up the DNA and histones, until it is 10 times shorter than during its resting state
Figure 9-4 Chromosome structure
DNA double helix
histone proteins
DNA woundaround histoneproteins
Loops attachedto a protein scaffold;this stage of partialcondensation typicallyoccurs in a nondividingcell
Coiled DNA/histone beads
protein scaffold
Foldedchromosome,fully condensedin a dividing cell
WHAT DO THE FOLLOWING TERMS MEAN? HOW ARE THEY RELATED?
DRAW THEM. DNA- GENES- SISTER CHROMATIDS- CENTROMERE CHROMOSOMES- HISTONES- LOCI- TELOMERE-
GENES, CHROMOSOMES, and DNA
The DNA in a chromosome consists of two long strands of nucleotides wound around each other, as a ladder would look if it was twisted into a corkscrew shape
This structure is called a double helix
The units of inheritance, called genes, are segments of DNA
The specific sequence of nucleotides in genes spells out the instructions for making the proteins of a cell
When a cell divides, it replicates its DNA to make two identical copies, and gives each daughter cell one of the two copies
9.3 How Is the DNA in Eukaryotic Chromosomes Organized?
Genes are segments of the DNA of a chromosome
Genes are sequences of DNA from hundreds to thousands of nucleotides long
Each gene occupies a specific place, or locus (plural, loci) on the chromosome
9.3 How Is the DNA in Eukaryotic Chromosomes Organized?
In addition to genes, every chromosome has specialized regions that are crucial to its structure and function Two telomeres One centromere The two ends of a chromosome consist of repeated nucleotide sequences called
telomeres, which are essential for chromosome stability
9.3 How Is the DNA in Eukaryotic Chromosomes Organized?
Genes are segments of the DNA of a chromosome (continued)
The second specialized region of the chromosome is the centromere, which has two principal functions
1. It temporarily holds two daughter DNA double helices together after DNA replication
2. It is the attachment site for microtubules that move the chromosomes during cell division
Eukaryotes Chromosomes carry the DNA…but you need
two IDENTICAL COPIES of DNA to go to the 2 cells
chromosome # varies between species
humans-46 chromosomes (23 pairs)
REMEMBER: The life of a cell
Before cells
can divide,
DNA needs to be replicated
So the code can be
passed on.
Which phase does this happen in????
DNA Replication
Process of copying a double stranded DNA to form 2 double stranded molecules
Basis of biological inheritance used by all living things
Occurs before a cell divides (mitosis)
DNA Replication
1. Enzymes break the hydrogen bonds between the bases so the chains of DNA can separate or unwind
2. Other enzymes add new nucleotides, which form new hydrogen bonds with their complimentary nucleotide.
Red = original strandBlue = new strand
DNA Replication
DNA Replication
Results in 2 semi-conservative double stranded molecules
WHAT IS THE ROLE OF:
Helicase-
SSB-
Replication fork-
DNA Polymerase-
ANIMATIONS OF DNA REPLICATION
http://www.bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.swf
http://www.mcb.harvard.edu/Losick/images/TromboneFINALd.swf
http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter11/animation_quiz_2.html
http://www.sinauer.com/cooper/4e/animations0601.html
AMEOBA SISTERS:https://www.youtube.com/watch?v=5qSrmeiWsuc&index=1&list=PLwL0Myd7Dk1F1pp-DaLx3ygO_7xA-yyd4